HSQLDB example source code file (ResourceStreamProvider.java)

This example HSQLDB source code file (ResourceStreamProvider.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - HSQLDB tags/keywords

classloader, classloader, hashset, inputstream, io, ioexception, ioexception, missing, net, network, resourcestreamprovider, resourcestreamprovider, set, string, url, url, wrong

The HSQLDB ResourceStreamProvider.java source code

/* Copyright (c) 2001-2008, The HSQL Development Group
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * Redistributions of source code must retain the above copyright notice, this
 * list of conditions and the following disclaimer.
 *
 * Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 *
 * Neither the name of the HSQL Development Group nor the names of its
 * contributors may be used to endorse or promote products derived from this
 * software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL HSQL DEVELOPMENT GROUP, HSQLDB.ORG,
 * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */


package org.hsqldb.lib;

import java.io.IOException;
import java.io.InputStream;
import java.net.URL;

import org.hsqldb.persist.Logger;

/**
 * An abstraction over the standard java.lang.Class.getResource[AsStream]() that
 * allows a superceding class loader to be injected at the top of the precedence
 * chain, for instance when the runtime must perform embedded resource loading
 * through a custom or non-standard protocol.
 *
 * @author boucherb@users
 * @version 1.8.1.3
 * @since 1.8.1.3
 */
public class ResourceStreamProvider {

    private static ClassLoader loader;
    private static HashSet     forbiddenProtocols = new HashSet();

    static {
        forbiddenProtocols.add("file");
    }

    private ResourceStreamProvider() {}

    public static synchronized void setLoader(ClassLoader loader) {
        ResourceStreamProvider.loader = loader;
    }

    public static synchronized ClassLoader getLoader() {
        return ResourceStreamProvider.loader;
    }

    public static Set forbiddenProtocols() {
        return forbiddenProtocols;
    }

    public static boolean exists(String resource) {

        ClassLoader loader = ResourceStreamProvider.getLoader();
        URL         url    = null;

        if (loader == null) {
            url = Logger.class.getResource(resource);
        } else {
            url = loader.getResource(resource);

            if (url == null) {
                url = Logger.class.getResource(resource);
            }
        }

        return url != null
               && !forbiddenProtocols().contains(url.getProtocol());
    }

    public static InputStream getResourceAsStream(String resource)
    throws IOException {

        ClassLoader loader = ResourceStreamProvider.getLoader();
        URL         url    = null;

        if (loader == null) {
            url = Logger.class.getResource(resource);
        } else {
            url = loader.getResource(resource);

            if (url == null) {
                url = Logger.class.getResource(resource);
            }
        }

        if (url == null) {
            throw new IOException("Missing resource: " + resource);
        }

        String protocol = url.getProtocol();

        if (forbiddenProtocols.contains(protocol)) {
            throw new IOException("Wrong protocol [" + protocol
                                  + "] for resource : " + resource);
        }

        return url.openStream();
    }
}